The present application relates generally to digital interfaces in integrated circuits, and more specifically to a multiplexed single-bit digital interface circuit.
In recent years, advancements in sub-micrometer Integrated Circuit (IC) design and manufacturing technology have led to drastic reductions in the physical size and cost of electronic devices. For example, in the field of audio signal processing, such advancements in IC design and manufacture have made it possible to include Analog-to-Digital Converters (ADCs) and powerful digital signal processing circuitry in a compact low-cost digital microphone device. A conventional digital microphone device typically includes an audio transducer, an analog input interface, an ADC, a clock generator, and a digital output interface. In a typical mode of operation, the audio transducer generates an analog signal representative of an audio input signal, and provides the analog signal to the analog interface, which may include one or more programmable gain amplifier circuits. Next, the analog interface circuit provides the analog signal to the ADC, which may comprise a sigma-delta ADC. The ADC then converts the analog signal into a corresponding digital signal, and provides the digital signal to the digital interface. The clock generator generates suitable clock signals for use by both the ADC and the digital interface. Finally, the digital interface circuit produces a digital output signal, which may then be provided to a user apparatus for subsequent reproduction of the audio input signal.
In today's compact electronic devices such as the conventional digital microphone described above, the functionality of the device must be provided to the user via a simple interface having a minimal number of external connections, terminals, and/or pins. However, this can be problematic in the digital microphone device because the digital microphone is often required to provide a digital output signal in the form of multiple high-speed data streams. Further, because the analog interface of the digital microphone may include programmable gain amplifiers, the digital microphone may also be required to provide gain control information in addition to the high-speed data streams. For this reason, the conventional digital microphone device frequently includes extra external connections, terminals, and/or pins to convey the data and gain control information, which can increase the complexity of the digital interface and thus the overall size and cost of the device.
It would therefore be desirable to have an improved digital interface that avoids the drawbacks of the above-described conventional digital interface circuitry.